Analysis of Noise Reduction Obtainable from the Redesign of a Mechanical Assembly

Abstract

A mechanical assembly which has been investigated experimentally for noise reduction (1)‡ is examined analytically. The assembly is reduced to a model of two unequal masses connected by a shaft. The redesigned version is the same except for the insertion of a rubber bush which isolates the larger mass, thereby reducing radiated noise. Only the longitudinal modes in which noise radiation was known to take place are considered for mathematical formulation. Vibrational amplitude spectra are derived for any point in the models. Amplitude spectra are substituted directly into the theory of sound radiation from a piston to calculate noise levels radiated by the larger mass. Experimental results are in good agreement with those obtained theoretically.